Ed,Horizontal is the name of the game. At some point, everything becomes horizontal. Go for it.

: We�re adding a new second floor bathroom on the opposite side of the house from the existing stack. Accordingly, I am planning to install a second stack line that ties into my sewer line in the basement floor. However, it will be impossible to have a fully vertical stack run. In fact, the new 3� DWV will need to run horizontally for about 20 feet across the basement ceiling (it will have at least 1/4" slope per horizontal foot) before running vertically through the first floor walls. Once it reaches the first floor ceiling it will run horizontally another 10 feet before running vertically through the second floor walls and out the roof.

: I�m fully aware of all the critical venting distances and will make sure that all drains into this stack have auxiliary vent lines that tie back into the stack in the attic. So I think everything will work fine � but just don�t recall ever seeing the sort of horizontal runs I�m planning. Thoughts?